1. Field of the Invention
The present invention relates to a howler indicator in a cordless telephone system comprising a master device and a mobile device, and more particularly, to a howler indicator which generates an alarm for prompting the operator to an on-hook action, i.e., generates a howler on the side of a mobile device.
2. Description of the Related Art
As well known, a cordless telephone system comprises a master device connected to a general subscriber's line leading to an exchange or switchboard and a mobile device connected through a radio line to the master device to allow the operator to have a conversation with the party through the mobile device.
A conventional cordless telephone system of the type referred to has been arranged so that when the mobile device is left in its OFF-HOOK state, a howler signal is applied from a switchboard through a general subscriber's line to the master device to warn the operator of the OFF-HOOK state of the mobile device, in which case the master device does not transmit the howler signal through the radio line to the mobile device but flashes a light emitting element LED or gives an alarm sound in accordance with the howler signal on the side of the master device to prompt the operator to hook on the mobile device or cut off the line of the mobile device. However, even when such indication of prompting the ON-HOOK action of the mobile device is provided on the side of the master device, it is disadvantageously impossible for the operator by the mobile device to know the indication so long as the mobile device is located away from the master device. In addition, when the line of the mobile device is cut off on the side of the master device, since the mobile device is left in its OFF-HOOK state, it becomes disadvantageously impossible to sound the mobile device at the time of receiving a new signal. In the prior art system, the howler signal is transmitted to the mobile device from the master device. However, the howler signal is much higher in level than a voice signal so that, for example, when a frequency-modulated (FM) signal is used as carried on the radio line, the direct transmission of the howler signal causes the level of the howling signal received at the mobile device to become remarkably low due to the limitation of the maximum frequency shift, thus disabling the sufficient informing function.
In this way, such a prior art cordless telephone system is arranged so that the indication of prompting the ON-HOOK action of the mobile device is provided on the side of the master device, which results in that when the mobile device is located away from the master device, the operator by the mobile device cannot know the indication. Moreover, the prior art system has such a problem that when the system is arranged to cut off the line of the mobile device on the side of the master device, the mobile device is left in the OFF-HOOK state, whereby the mobile device cannot sound at the time of a signal reception.